You try it! Smoothed Particle Hydrodynamics (SPH) Bird strike example For more information (including the model files), see the associated SIMULIA e-Learning Resource https://swym.3ds.com/#post:8663
These instructions were created using Abaqus 6.11 Use Smoothed Particle Hydrodynamics (SPH) to simulate a bird strike example in which a bird (in the form of a cylindrical projectile) hits an airplane engine blade.
Run script v_sph_birdstrike.py to create the blade model, which is built using conventional shell elements. Proceed with the creation of the bird, to be modeled with SPH elements, as described below. 1. Create the BIRD geometry First, create a deformable part to model the bird. Use an aproximat part size of 1. Sketch a circle and specify a radial dimension of 0.04 m. The height of the extruded cylinder will be 0.076 m.
© Dassault Systèmes, 2012
www.3ds.com/simulia-learning
2. Create an auxiliary continuum solid mesh Before meshing the newly created part, partition the cylinder in half using the Normal To Edge method.
Once this is done, I can mesh the BIRD using continuum brick elements (C3D8R). Set the approximate global mesh size to 0.005 (equal to the size of a small cube at each SPH particle.) To produce as uniform a mesh as possible use the Medial axis mesh algorithm with minimized mesh transitions.
Note that the SPH method can be used to model bodies of any size. The particle size used in SPH applications is arbitrary. o However, the smaller the particle size the more detailed the result. 3. Create a node set that includes all the BIRD nodes Next, Create a part-level set containing all the BIRD nodes; this will be used in the next step to create point masses and later to define a node-based BIRD surface.
© Dassault Systèmes, 2012
www.3ds.com/simulia-learning
4. Create mass elements at the nodes of the auxiliary mesh Switch to the Property module and create point masses with an arbitrary mass value at each node of the auxiliary mesh.
Note that Abaqus/CAE displays green square glyphs to indicate the presence of mass elements at the nodes. 5. Create material In this example, the material properties of the bird are described by a tabular equation of state, which is not directly supported by Abaqus/CAE. The Keyword editor was used in the setup script to define the tabular equation of state material.
© Dassault Systèmes, 2012
www.3ds.com/simulia-learning
6. Instance the BIRD part Next, instance the BIRD part in the Assembly module and translate it using a start point of 0,0,0 and an end point of 0.6514, -0.1354, -0.048
7. Apply initial velocity to the BIRD Now, apply translation velocity to all the nodes of the BIRD in the global 3-direction.
© Dassault Systèmes, 2012
www.3ds.com/simulia-learning
8. Request the field and history output Next, create a part-level node set, to request history output at a central point on the projectile base that is closest to the blade.
Once the set is defined, create a History output request for displacements.
© Dassault Systèmes, 2012
www.3ds.com/simulia-learning
This completes the Abaqus/CAE portion of the model preparation.
Switch to the Job module, write the input file, and leave Abaqus/CAE open for later visualization of the analysis results.
9. Now manually modify the input file produced by Abaqus/CAE.
1. In a text editor, start by Removing the auxiliary continuum solid elements (C3D8R) from the file
2. Then Change the MASS elements to PC3D particle elements
Becomes:
3. Remove the dummy *MASS keyword option from the file
© Dassault Systèmes, 2012
www.3ds.com/simulia-learning
and in its place use the *SOLID SECTION option to associate the particle elements with the material defined previously in Abaqus/CAE.
Note that the characteristic length associated with the particle volume is half the side of the small cube associated with each SPH particle. Recall that when I meshed the bird, I specified an approximate global mesh size of 5 mm, so the characteristic length given here is 2.5 mm
4. Next, define a node-based surface that includes all the SPH particles using the part level node set defined earlier Abaqus/CAE
Recall that particle elements do not have faces or edges; therefore, I must use a node-based surface rather than an element-based surface.
5. Finally, define contact interactions between the particle surface and the aircraft engine blade.
Now the input data preparation is complete. 10. run the analysis using the command line. >abaqus –job birdStrike
© Dassault Systèmes, 2012
www.3ds.com/simulia-learning
11. After the job completes, study the results in the Abaqus/CAE Visualization module. First, visualize the blade deformation as a result of the impact with the bird using the time history animation.
Note that the elements in the set Part-1-1.CONTACTOUTERBOX have been removed from the view.
Next, contour the stress distribution in the cylindrical projectile at specific time points.
© Dassault Systèmes, 2012
www.3ds.com/simulia-learning
Note that the values of field output variables are shown as circular patches of color in contour plots. Use symbol plots to visualize distributions of various vector fields such as velocity.
Finally, create a history plot of the turbine hub displacement. The plot clearly shows that for the blade design under consideration, the hub displacements resulting from the bird impact are formidable.
© Dassault Systèmes, 2012
www.3ds.com/simulia-learning
